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Shimo, Michito*; Kumamoto, So*; Ito, Akira*; Karasaki, Kenji*; Sawada, Atsushi; Oda, Yoshihiro; Sato, Hisashi
JAEA-Research 2010-040, 57 Pages, 2010/11
JAEA-Research-2010-040.pdf:5.12MB
In safety analysis of geological disposal of the high-level nuclear waste, it is important to evaluate appropriately the mass transport characteristics of the bedrock as the natural barrier. Especially, it has been found that the porosity of the rock matrix is high and fractured zones are developing and therefore the mass transport characteristics will be the mixture of those for porous media and the fractured media. In this work, we conducted, (1) a study on the method to mine out the rock block sample of tens of-centimeter to maximum 1 m scale, (2) a study on a method of the tracer test using a rock block sample and a series of scoping analysis. We also examined the uncertainty associated the hydrogeological model using a method combining a forward and inverse analysis, based on the various type of data sets obtained at Horonobe site, such as the temperature distribution and hydraulic head and salinity distribution.
Shimo, Michito*; Kumamoto, So*; Ito, Akira*; Karasaki, Kenji*; Sawada, Atsushi; Oda, Yoshihiro; Sato, Hisashi
JAEA-Research 2009-060, 70 Pages, 2010/03
JAEA-Research-2009-060.pdf:14.26MB
It is important for safety assessment of HLW geological disposal to evaluate groundwater flow and mass transport in deep underground appropriately. Though it is considered that the mass transport in sedimentary rock occurs in pores between grains mainly, fractures of sedimentary rock can be main paths. In this study the following three tasks were carried out: (1) laboratory hydraulic and tracer experiments using the rock cores of Wakkanai formation, (2) a study on the tracer test and sampling technique for the larger scale, (3) a study on the reduction technique of uncertainty of the hydrogeological models using data from surface-based investigation. On the block scale tracer test technique, the sampling technique using wire saw and tracer test technique using block samples were suggested. As for the reduction technique of uncertainty of the hydrogeological model, availability of the information other than pressure data, such as the temperature and salinity and all, were presented.
Karasaki, Kenji*; Ito, Kazumasa*; Wu, Y.*; Shimo, Michito*; Sawada, Atsushi; Maekawa, Keisuke; Hatanaka, Koichiro
Proceedings of TOUGH Symposium 2009 (Internet), 9 Pages, 2009/09
Shimo, Michito*; Kumamoto, So*; Karasaki, Kenji*; Sato, Hisashi; Sawada, Atsushi
JAEA-Research 2008-101, 70 Pages, 2009/03
JAEA-Research-2008-101.pdf:7.03MB
It is important for safety assessment of HLW geological disposal to evaluate groundwater flow and mass transport in deep underground. The fractures might dominate flow and transport even though it is soft sedimentary rocks. In this study the following three tasks were carried out. Firstly, non-sorbing tracer experiments were carried out. The obtained breakthrough curve was interpreted and mass transport parameters, such as longitudinal dispersivity, matrix diffusion coefficient, transport aperture, were obtained. Secondary, several cases mass transport simulations using single fracture model that the hydraulic aperture, transport aperture, and porosity is different were performed to study on the influence that a difference of the aperture and porosity gives a mass transport in the fractured sedimentary rocks. Finally, groundwater flow was simulated to estimate the flow direction and recharge from the surface using the temperature distribution data obtained in Horonobe boreholes.
Ijiri, Yuji*; Saegusa, Hiromitsu; Sawada, Atsushi; Ono, Makoto*; Watanabe, Kunio*; Karasaki, Kenji*; Doughty, C.*; Shimo, Michito*; Fumimura, Kenichi*
Journal of Contaminant Hydrology, 103(3-4), p.168 - 181, 2009/01
Times Cited Count：9 Percentile：30.23(Environmental Sciences)Qualitative evaluation of the effects of uncertainties originating from scenario development, conceptual models, and parameter values is an important subject in the area of safety assessment for high-level nuclear waste disposal. In this study, regional-scale groundwater flow analyses for the Tono area, Japan were conducted using three continuous models which were designed to handle heterogeneous porous media. We evaluated the simulation results to quantitatively analyze uncertainties originating from conceptual models. We found that uncertainties originating from conceptual models (1) greatly depend on boundary conditions and hydrological structures to be modeled, which are assigned by modelers, and (2) are larger than uncertainties originating from the variance in realizations of the Monte Carlo method in stochastic modeling.
Shimo, Michito*; Kumamoto, So*; Karasaki, Kenji*; Sawada, Atsushi; Maekawa, Keisuke; Sato, Hisashi
JAEA-Research 2008-029, 95 Pages, 2008/03
JAEA-Research-2008-029.pdf:4.51MB
It is important for safety assessment of HLW geological disposal to evaluate groundwater flow and mass transport in deep underground accurately. The objective of this study is to expand the data of flow and mass transport properties in fractured sedimentary rocks, and to estimate these properties in larger scale rocks, such as in situ test scale, using the results of the laboratory tests and the borehole investigations. This study was carried out under the following three tasks: (1) laboratory hydraulic and tracer experiments using the rock specimens of Koetoi formation obtained at underground research facility under construction in the Horonobe area, (2) a numerical study on the influence that a difference of the groundwater flow velocity in the fractures gives a mass transport in the fractured sedimentary rocks, (3) a numerical study on the contributing factors to groundwater flow such as effect of low permeability layers.
Nomoto, Kosuke*; Matsui, Mikio*; Inoue, Hiroyuki*; Yoshino, Naoto; Karasaki, Kenji*; Ito, Kazumasa*
JNC TJ8400 2005-005, 94 Pages, 2005/02
JNC-TJ8400-2005-005.pdf:7.92MB
In the safety assessment at geological disposal of High Level Nuclear Waste, it is necessary to understand several properties like hydrological, geological and chemical properties of the disposal site by site investigations. The investigation results should project to the ground water flow modeling, migration modeling and the parameter assignment of these models. Japan Nuclear cycle Development Institute is going to carry out two Underground Research Laboratory plans in order to push on with the project and help to make up the safety criteria of the geological disposal. Horonobe is one area of these plans. In Horonobe, following properties were identified./-There are saline and fresh water./-There is dissolved gas in the underground water./-The underground of some area has high water pressure./In this study, the analysis considering above properties were carried out for understanding of hydrological properties in sedimentary rock. In addition, the affection to the water flow and migration influenced by the results were examined.
Tsang, C.-F.*; Karasaki, Kenji*
JNC TY8400 2001-006, 224 Pages, 2001/07
JNC-TY8400-2001-006.pdf:6.92MB
None
Tsang, C.-F.*; Karasaki, Kenji*
JNC TY8400 2000-007, 279 Pages, 2000/07
JNC-TY8400-2000-007.pdf:7.62MB
None
Tsang, C.-F.*; Karasaki, Kenji*
JNC TY1400 2005-012, 661 Pages, 1997/03
Karasaki, Kenji*; Ito, Kazumasa*; Maekawa, Keisuke
no journal, ,
We have modeled laboratory experiments of saltwater intrusion using TOUGH2/EOS7. Matching laboratory and simulation results turned out to be quite challenging partly because of numerical dispersion and partly because the experiments were not very well controlled. In order to understand better the effects of numerical dispersion, we simulated the so-called Henry problem, in which a large dispersion coefficient is assumed, resulting in a wide transition zone between freshwater and saltwater. We imposed a sinusoidal boundary condition to see if a large transition zone can be created without explicitly modeling dispersion. However, for the parameters used we were not able to do so. It is still plausible that a wide transition zone is caused by formation heterogeneity and transient effects. Nonetheless, we question the validity of the use of a large dispersion coefficient where the velocity is very low, or where the flow is in the opposite direction of the concentration gradient.
Maekawa, Keisuke; Karasaki, Kenji*; Ito, Kazumasa*
no journal, ,
As a study to comprehend geological environment, we examined numerical analysis in order to understand the behavior of saltwater intrusion. This is an important study for safety assessment of high level radioactive waste geologic disposal. We made sense a relation between an extent of numerical dispersion and various grid spacing in analytical region. And the analytical code was verified with an experiment under the simple condition.
Maekawa, Keisuke; Karasaki, Kenji*; Takasu, Tamio*
no journal, ,
no abstracts in English
Maekawa, Keisuke; Karasaki, Kenji*; Takasu, Tamio*
no journal, ,
It is important for safety assessment of high-level radioactive waste geologic disposal to understand groundwater flow in deep underground accurately. In order to understand the behavior of seawater intrusion into freshwater in deep underground, we constructed a laboratory equipment, "Mini-MACRO" (MAss transport Characterization in host ROck). We created several cases of experimental conditions to observe the seawater intrusion behavior into two-layered stratum against various hydraulic gradients and densities of saltwater. We confirmed that the results using this equipment match numerical results under simple heterogeneous condition.
Karasaki, Kenji*; Maekawa, Keisuke
no journal, ,
We have modeled laboratory experiments of saltwater intrusion, similar to the so-called Henry Problem, using TOUGH2/EOS7. In general, the simulation showed good agreement to the experiment including the transient advancement and the final profile of the saltwater wedge that showed little dispersion in a homogeneous case. In a two-layer heterogeneous case, however, the simulation could not reproduce the experiment in one aspect. In the experiment, the fast-moving colored saltwater traveling in the higher permeability layer was observed encroaching into the lower permeability layer below. However, at this writing, we have not been able to reproduce this phenomenon, which could be caused by some instability or heterogeneity within the layers.
